In general, a pneumatic tire is required to have high fuel efficiency and excellent steering stability on wet road surfaces. Therefore, a large amount of silica is added to a tire tread rubber composition constituting a tread to provide the rubber composition with a decreased rolling resistance and an enhanced wet grip performance. However, the silica-containing rubber composition has a problem of decreased abrasion resistance.
Patent Document 1 proposes a tire rubber composition for improving low rolling resistance and wet grip performance. This rubber composition is prepared by adding silica to a rubber component including natural rubber, solution-polymerized styrene-butadiene rubber, and emulsion-polymerized-styrene butadiene rubber. However, such a rubber composition insufficiently meets the users' demands for three functionalities: low rolling resistance, wet grip performance, and abrasion resistance. Therefore, these three functionalities of the tire rubber composition have been desired to be improved to higher levels, respectively.